This invention relates to a combustible pellet forming system and to a dryer therefor, particularly a dryer having the capability of driving off volatilizable substances from particulate materials such as wood chips, sawdust, ground leaves and the like, condensing and retaining these substances. It is also useful as a kiln for lumber.
Disposal of organic substances such as tree branches and leaves has been given serious consideration in recent years, partially because of increasingly limited landfill space available, restrictions on residential burning of leaves, etc. One technique used to process tree branches is to chip them into pieces. A small percentage of these wood chips and leaves is presently used for mulch. Another portion of the wood chips is used to power generators of electricity in large commercial/industrial units. Still, there remains a tremendous amount of chips and leaves which cannot presently be used for these purposes. Some cities have resorted to paying significant sums to have such materials hauled away and composted. While this is a commendable practice, it is expensive and certainly not a total solution.
Another costly factor experienced by persons living in colder climates such as the northern part of the United States, and elsewhere, is the purchase of fuel including natural gas, propane gas, fuel oil and wood. In the past, wood for fuel has been largely in the form of cord wood, i.e., large pieces which are cut, split and manually handled. An alternative to this is the growing use of uniform size, compressed wood pellets which can be manually or automatically fed into a special stove or stoker furnace built to accommodate the pellets. However, for such pellets to be the most efficient, the moisture contained by the pellets should be low. Hence, there is need for efficient drying. As to leaves, of which there is an abundance every autumn, a substantial share of these have found no market at all, such that they largely constitute a nuisance for which disposal is costly.
Another use of dryers where fuel consumption is substantial is the drying of farm food products such as grain and corn. The fuel required is substantial and costly with present equipment.